Intravascular diseases are commonly treated by relatively non-invasive techniques such as percutaneous transluminal angioplasty (PTA) and percutaneous transluminal coronary angioplasty (PTCA). These therapeutic techniques are well-known in the art and typically involve the use of a balloon catheter with a guide wire, possibly in combination with other intravascular devices. A typical balloon catheter has an elongate shaft with a balloon attached to the distal end and a manifold attached to the proximal end. In use, the balloon catheter is advanced over the guide wire such that the balloon is positioned adjacent a restriction in a diseased vessel. The balloon is then inflated and the restriction in the vessel is opened.
There are two basic types of balloon catheters used in combination with a guide wire, namely, over-the-wire (OTW) catheters and single-operator-exchange (SOE) catheters. The construction and use of both OTW catheters and SOE catheters are well-known in the art. An example of an OTW catheter may be found in commonly-assigned U.S. Pat. No. 5,047,045 to Arney et al. An example of an SOE balloon catheter is disclosed in commonly-assigned U.S. Pat. No. 5,156,594 to Keith.
PTA and PTCA catheters are preferably designed to optimize pushability, trackability and crossability. Pushability is defined as the ability to transmit force from the proximal end of the catheter to the distal end of the catheter. Trackability is defined as the ability to navigate tortuous vasculature. Crossability is defined as the ability to navigate the balloon catheter across narrow restrictions in the vasculature.
OTW balloon catheters may be classified into two groups. The first group comprising multi-lumen OTW balloon catheters, and the second group comprising coaxial OTW balloon catheters. Multi-lumen OTW catheters typically include a single extrusion shaft having two side-by-side longitudinally extending lumens, namely an inflation lumen and a guide wire lumen. By contrast, a coaxial OTW catheter typically includes two separate tubes, namely an inner tube and a coaxially disposed outer tube. The inner tube defines a guide wire lumen and an annular inflation lumen is defined between the inner tube and the coaxially disposed outer tube.
Prior art coaxial OTW-type balloon catheters have attempted to maximize pushability by incorporating a stainless steel outer tube on the proximal shaft (also referred to as a hypotube). However, because of the relatively large outside diameter to wall thickness ratio and the relatively low yield strain of stainless steel, such a shaft construction is more prone to kinking than a typical polymer shaft. Currently-marketed coaxial OTW-type balloon catheters typically incorporate a polymer shaft or a reinforced polymer shaft (e.g. composite) as a compromise between maximizing pushability and minimizing the probability of kinking. As such, there is an unmet need for a coaxial OTW-type balloon catheter which satisfies the need for both maximum pushability and minimum propensity to kink.
Prior art OTW and SOE-type balloon catheters have also attempted to improve crossability by minimizing the profile of the deflated balloon. State-of-the-art balloon catheters have a balloon profile which is typically limited by the profile of the distal balloon waist and/or the profile of the balloon at the location of the marker band. Accordingly, it is desirable to have OTW and SOE-type balloon catheters which minimize the profile of the distal balloon waist and minimize the profile of the balloon over the marker band in order to maximize crossability.